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Ti-doped diamond-like carbon (Ti-doped DLC) films were deposited on 304 stainless steel through a pulsed filtered cathodic vacuum arc deposition with an individual cathodic arc source. Structural dependent thermal stability, mechanical properties, adhesion, and corrosion performance were thoroughly investigated as a function of the Ti content. Only 0.8 at.% Ti content in the DLC films offers the relatively high hardness (28.8 GPa), high corrosion resistance, enhanced adhesion strength as well as improved thermal stability compared to the undoped DLC films. The reduction in the internal stress and the sp3 content associated with a slight decrease in the mechanical properties is from Ti doping. Higher thermal stability is due to the TiC phase in the Ti-doped DLC structure. Enhancement of the adhesion strength is owing to the relief of the internal stress and the occurrence of the strong atomic intermixing bond at a Ti-doped DLC/Ti intermediate layer interface. Interestingly, the formation of the TiO2 film on the Ti-doped DLC surface due to a small amount of Ti doping significantly exhibited a better corrosion performance. Ti-doped DLC films, therefore, are a promising coating for tribological applications.

Diamond-like carbon (DLC) films were deposited by pulsed filtered cathodic vacuum arc (FCVA) deposition. The microstructure, mechanical and optical properties of DLC films have been investigated as functions of the variation in the substrate negative direct current bias voltage (Vbias) from 0.0 to 1.5 kV. Raman and X-ray photoelectron spectroscopy results show a correlation between the ID/IG ratio and the microstructure in terms of the sp3/sp2 ratio to Vbias. This fact shows that a significant change in the sp3 content, which is attributed to the transformation from graphite-like to diamond-like, is accompanied by a decreasing ID/IG ratio. The relatively high mass density of the films in the range of 2.51 to 2.79 g/cm3 can be obtained with biasing. The mechanical properties, i.e., the hardness and elastic modulus, were 13–25 and 114–145 GPa, respectively. The improvement of the mechanical properties is due to the formation of the compressive residual stress and the local density depending on Vbias. The relationship between the refractive index and the ID/IG ratio agree well with the microstructure and mechanical properties of DLC films. All of these results indicate a vital role of Vbias in determining the DLC properties.

Titanium was incorporated and interlayered into diamond-like carbon (DLC) films deposited on 316L stainless steel using a filtered cathodic vacuum arc. The local bonding structure, corrosion, and biocompatibility of non-doped DLC (ta-C), Ti-interlayered (ta-C/Ti), Ti-doped (ta-C:Ti), and Ti-doped and Ti-interlayered (ta-C:Ti/Ti) DLC films were thoroughly investigated. ta-C:Ti/Ti (0.55 at.%Ti) exhibited not only the highest corrosion resistance performance, including the lowest corrosion rate (7.34 × 10−8 mm yr−1), the highest pitting potential (1672.97 mV), and the highest polarization resistance (5.97 MΩ cm2), owing to the formation of TiO2 on its surface, as confirmed by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, but also the highest amount of hydroxyapatite, an indicator for biocompatibility, on its surface as determined with Fourier transform infrared spectroscopy and scanning electron microscopy. Two barrier layers, namely, outer and inner layers, were observed in ta-C/Ti and ta-C:Ti/Ti, while only one barrier layer was in ta-C and ta-C:Ti, as demonstrated by electrochemical impedance spectroscopy. Therefore, ta-C:Ti/Ti is an alternative promising DLC film for joint replacement biomaterials.

Al and N were incorporated into diamond-like carbon (DLC) films deposited using a filtered cathodic vacuum arc on AISI 4140 low-alloy steel. The structure, nanomechanical properties, local bonding, and thermal stability of non-doped DLC (ta-C), Al- and N-doped (ta-C:Al and ta-C:N), and Al- and N-co-doped (ta-C:Al:N) films were thoroughly investigated. The thermal stability of the deposited films was measured using radiative heating and electron beam bombardment under a vacuum during thermal annealing. In-situ near-edge X-ray absorption fine structure spectroscopy was performed to characterize the surface nanostructures at different temperatures. ta-C:Al:N exhibited not only high hardness (49.04 GPa) and high (58.43%) elastic recovery (ER)—approximately equal to those of non-doped DLC films: 51.12 GPa and 60.06% ER, respectively)—but also higher thermal stability than ta-C at ~600 °C owing to the synergy of Al2O3 and sp3 N-C bonds formed in the DLC films, as confirmed by X-ray photoelectron spectroscopy. ta-C:Al:N, therefore, is a suitable coating for wear and tribological applications, especially at high temperatures.

The erosion-corrosion behaviors of 1045 and J55 steels in crude oil with a variation in sand sizes between 500 and 2000 μm were studied using the impingement jet system incorporated with an electrochemical measurement and were characterized with a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and an inductively couple plasma-optical emission spectrometer (ICP-OES). All the erosion-corrosion results agreed well with the ICP-OES measurement that the released iron ions increase with the high wastage of steels, particularly for the 1045 steel, which showed a greater number of released iron ions and a higher penetration rate than the J55 steel. The degree of synergism between the erosion and corrosion drastically changed with the impingement sand size and the microstructure of the steels. The XPS results showed a notable correlation between the erosion-corrosion behaviors and the compounds generated after the wastage of the specimens. A high atomic percentage (at%) of SiO2 and the high amount of C O C + C O were found on the highly degraded-surface. Classification of the degradation mode was made distinct by considering the Fe(II)/Fe(III) atomic ratio. A high ratio of the Fe(II)/Fe(III) compounds represents better pure erosion resistance, whereas a low ratio demonstrates better pure corrosion resistance and total corrosion component resistance.

This work studied the corrosion behaviors of 15Ni, 23Ni, 31Ni and 40Ni steels in aerated 3.5% NaCl solutions at pH 2, 7, 10 and temperature of 25ºC. The observed microstructures of 15 and 23 wt.% Ni steels were partially martensite, but those of 31 and 40 wt.% Ni steels were fully austenite. Polarization curves of the nickel steels were measured by potentiodynamic technique. The corrosion potential (Ecorr), corrosion current density (Icorr), from which the corrosion rate (Rmpy) was calculated, pitting potential (Ep), primary passive potential (Epp) and passive current density (Ip) were evaluated form the polarization curves. The results showed that increasing nickel content increased the corrosion potentials but decreased the corrosion current density or the corrosion rate. Only pH 10, the passive characteristics of the 23Ni, 31Ni and 40Ni steels were observed. The pitting potentials and primary passive potentials of those three steels increased with nickel contents, but the passive current density decreased. Nickel improved general corrosion and pitting corrosion resistances of the tested steels in basic, neutral and acid 3.5% NaCl solutions. The effects of nickel and solution pH on general corrosion resistances of nickel steels were discussed.

TiAlN films with thicknesses of 250, 500 and 750 nm were deposited on 4140 steel using the reactive direct current co-unbalanced magnetron sputtering method. The effects of the film thickness on the microstructure were revealed using a field emission scanning electron microscope, an image analyzer and X-ray diffraction. The results showed that grain size apparently increased when the film was at greater thicknesses whereas porosity, lattice strain and dislocation density decreased. Meanwhile, the results of anodic polarization tests in air-saturated 3.5 wt.-% NaCl solution at pH levels of 2, 7 and 10 and at 25 °C showed lower corrosion potential in thicker film, attributed to a lower ratio of grain boundary area to individual grain area. However, a more stable passive film with higher pitting potential was formed. By analyzing using X-ray absorption spectromicroscopy, oxidation of Ti into TiO2 was found on the corroded surface of TiAlN film.

A cemented carbide end mill was coated with AlCrTiSiN film by cathodic arc physical vapor deposition methods (CAPVD). A performance of AlCrTiSiN film for increasing tool life was evaluated by scratch test, cutting test and oxidation test in comparison with uncoated end mill. From the scratch test, the AlCrTiSiN film was helpful to resist crack and delamination of coating. From the cutting test, the maximum flank wear of AlCrTiSiN film was about two times higher than that of the uncoated end mill resulting in tool life extension. From the oxidation test, the first oxide of AlCrTiSiN film generated after service life was a titanium dioxide (TiO2) at a temperature of 900oC. From all of results, it revealed that the AlCrTiSiN film significantly enhanced the tool life of the cemented carbide end mill.

Corrosion behaviors and mechanical properties of CrN film were evaluated. The CrN film was deposited on the surface of H13 steel by the magnetron sputtering method. The corrosion behaviors of the uncoated and CrN coated samples were studied in air-saturated 3.5 wt.% NaCl solution with various solution pHs, i.e., pH 2, 7 and 10 at 27°C by the electrochemical technique. The mechanical properties of the CrN coated samples were evaluated using nanohardness, ball on disk and scratch testers. The results revealed that the CrN coated samples had higher corrosion resistance than the uncoated samples at all pHs. Smooth substrate roughness enhanced corrosion resistance and also decreased the wear rate of the CrN coated samples on H13 steel. Corroded area was evaluated by synchrotron X-ray photoemission electron spectroscopy. It revealed that corrosion resistance of the CrN film was from oxidation of Cr into Cr2O3.

The objective of this research is to study wear behaviors of TiN, nanolaminated AlCrN and nanocomposite TiAlSiN coated on cemented carbide end mill deposited by cathodic arc physical vapor deposition methods in comparison with uncoated end mill. Wear behaviors were investigated by nanoindentation hardness test, scratch test and cutting test. Oxidation test was also done in air at temperatures of 700°- 900°C in order to evaluate resistance of oxidation. In the nanoindentation hardness and scratch tests, nanocomposite TiAlSiN coating exhibited higher hardness than TiN and nanolaminated AlCrN coatings. The nanolaminated AlCrN coating represented the highest adhesion ability in terms of critical load and the lowest coefficient of friction in comparison with the TiAlSiN and TiN coatings, respectively. The cutting performance, represented in terms of maximum flank wear as a function of cutting length, was found to be highest in the AlCrN coating. Oxides of these coatings, i.e., TiO2 for TiN, TiO2 for TiAlSiN and Cr2O3 for AlCrN, generated at different temperatures of 700°, 800° and 900°C, respectively. From all of results, it is obvious that the AlCrN coating exhibited more excellent wear resistance and oxidation resistance than the uncoated end mill, TiN coating and TiAlSiN coating.

Decorative Ni-Cr plating on ferritic stainless steel was exposed to pure carbon dioxide (CO2) at 200 and 300oC for 180 hours under continuous and cyclic oxidation tests. After oxidation test, weight changes of samples exposed to CO2 were found to be less than that of samples exposed to air. However, weight changes were dependent on temperature and oxidation conditions. Heat-quench test was operated at temperature of 200-500oC for determining adhesion behavior of decorative Ni-Cr plating. From the heat-quench test, it revealed that adhesion ability between Ni-Cr plating layer and substrate increased with thickness of Ni pre-plating layer at temperature of 200 and 300°C. But, at temperature above 300°C, the adhesion ability increased with surface roughness of substrate before coating. In order to achieve important properties of decorative Ni-Cr plating, i.e., oxidation resistance, beautiful appearance and good adhesion, surface of substrate was necessarily prepared under medium roughness and then it was pre-plated with the thickest Ni layer before Cr coating was applied.

Although the phenomenon of hydrogen assisted cold cracking (HACC) and respective avoidance procedures have extensively been investigated in the seventies and eighties, the reasons for recent failures are still a lack of knowledge about the basic hydrogen effects on steel microstructures and, in particular, a lack of welding procedure specifications and standards accounting directly and consistently for cold cracking avoidance in modern high strength structural steels with yield strengths of up to 1 100 MPa. In previous several contributions the consequences of various heat treatment procedures targeted at HACC avoidance have been shown, as for instance their effects on stress-strain build up and on hydrogen diffusion in high strength steel welds. But, a principal interaction of three local influences on hydrogen assisted cold cracking, i.e. local microstructure; local mechanical load and local hydrogen content have not yet been studied in detail for these materials. For this, a numerical model for HACC has been developed, accounting particularly for crack-initiation and crack-propagation criteria, like the hydrogen redistribution during the process of cracking. The numerical model has been used to investigate HACC in such materials, i.e. in the weld microstructures of an S 1100 QL steel, under severe restraint and various hydrogen levels. The results were achieved by in depth thermal and structural finite element simulations combined with numerical hydrogen diffusion modelling. By such procedure, HACC in single-layer welded plates with thickness of 20.0 mm at realistic restraints has been studied. As a particular result, it turned out that the crack-initiation location is typically in the centre of the weld metal (WM), where only a single crack is initiated at hydrogen contents of up to 10.0 Nml/100 g Fe. But, it was evidently shown by such analyses that the crack-initiation location is shifted into the HAZ and that multiple cracking occurs at higher hydrogen contents of up to 15.0 Nml/100 g Fe.

Corrosion behavior of diamond-like carbon (DLC) films was evaluated via potentiodynamic polarization in a 3.5 wt. % NaCl solution with pH 2 at room temperature. The polarization results elucidated that the corrosion resistance of the films was enhanced with the variation of the chemical compositions and film thicknesses. The use of the spectromicroscopy method in the investigation of the pitting corrosion was a success in this study. Formation of orbital mapping, bonding state, and composition of the DLC films at non-corrosion and corrosion areas indicate the different structures between DLC and graphite oxide. Also, the π* (C=C) and π* (C=O) bonding states were found to increase in the corrosion areas. This finding not only exhibited the increase of sp2 content but also promoted the rise of oxygen atoms in corrosion zones. Consequently, the present results indicate that the synchrotron–based spectromicroscopy plays an important role in the characterization of the corrosion on DLC films.